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습식환원법에서 NaBH<sub>4</sub>환원제를 이용한 Ag분말의 제조
원창환,이혁희,Won Chang-Whan,Lee Huk-Hee 한국분말야금학회 2006 한국분말재료학회지 (KPMI) Vol.13 No.4
Spherical Ag powder was prepared in the system of $AgNO_3\;and\;NaBH_4$ by wet chemical reduction method. The size of Ag powder was increased as the reaction temperature and the concentration of reducing agent was decreased in the constant concentration of dispersion agent. Optimum conditions of producing Ag powder having $1.39{\mu}m$ of D50 was 1M of $AgNO_3$, 0.5M of $NaBH_4$, 1.5g of Gelatine in the room temperature.
Ti−TiH<sub>2</sub>−C−N<sub>2</sub>계에서 연소반응에 의한 TiC<sub>0.7</sub>N<sub>0.3</sub> 분말의 제조
신창윤,원창환,Shin, Chang-Yun,Nersisyan, Hayk,Won, Chang-Whan 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.1
The preparation of $TiC_{0.7}N_{0.3}$ powder by SHS in the system of $Ti-TiH_2-C$ ($N_2$ atmosphere) was investigated in this study. In the preparation of $TiC_{0.7}N_{0.3}$ powder, the effect of gas pressure, compositions such as Ti, $TiH_2$, C, and additive in mixture on the reactivity were investigated. At 50 atm of the initial inert gas pressure in reactor, the optimum composition for the preparation of pure $TiC_{0.7}N_{0.3}$ was $0.75Ti+0.25TiH_2+0.7C+0.5NaCl$. The $TiC_{0.7}N_{0.3}$ powder synthesized in this condition was a single phase with irregular shape.
Al-AlN-NH<sub>4</sub>Cl 계에서 연소반응에 의한 AlN 분말의 제조
민현홍,원창환,Min, Hyun-Hong,Won, Chang-Whan 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.7
The preparation of AlN powder by SHS in the system of $Al-AlN-NH_4Cl$ was investigated in this study. In the preparation of AlN powder, the effect of gas pressure and the composition such as Al, AlF, and additive in mixture on the reactivity were investigated. At 60 atm of the initial inert gas pressure in reactor, the optimum composition for the preparation of pure AlN was 35 wt%Al+5 wt% $NH_4Cl+60wt%$AlN. The AlN powder synthesized in this condition was a single phase AlN with a whisker morphology.
고상법을 이용한 Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:Ce<sup>3+</sup>의 제조에서 BaF<sub>2</sub>가 미치는 영향
원형석,원창환,원형일,Won, Hyung-Seok,Hayk, Nersisyan,Won, Chang-Whan,Won, Hyung-Il 한국재료학회 2011 한국재료학회지 Vol.21 No.11
The effect of $BaF_2$ flux in $Y_3Al_5O_{12}:Ce^{3+}$(YAG:Ce) formation was investigated. Phase transformation of $Y_3Al_5O_{12}$(YAG) was characterized by using XRD, SEM, and TEM-EDS, and it was revealed that the sequential formation of the $Y_4Al_2O_9$(YAM), $YAlO_3$(YAP) and $Y_3Al_5O_{12}$(YAG) in the temperature range of 1000-1500$^{\circ}C$. Single phase of YAG was revealed from 1300$^{\circ}C$. In order to find out the effect of $BaF_2$ flux, three modeling experiments between starting materials (1.5$Al_2O_3$-2.5$Y_2O_3$, $Y_2O_3$-$BaF_2$, and $Al_2O_3$-$BaF_2$) were done. These modeling experiments showed that the nucleation process occurs via the dissolution-precipitation mechanism, whereas the grain growth process is controlled via the liquid-phase diffusion route. YAG:Ce phosphor particles prepared using a proposed technique exhibit a spherical shape, high crystallinity, and an emission intensity. According to the experimental results conducted in this investigation, 5% of $BaF_2$ was the best concentration for physical, chemical and optical properties of $Y_3Al_5O_{12}:Ce^{3+}$(YAG:Ce) that is approximately 10-15% greater than that of commercial phosphor powder.
리튬이온전지용 LiMn<sub>2</sub>O<sub>4</sub>분말의 자전연소합성시 반응변수의 영향
장창현,원창환,권혁상,Jang, Chang-Hyun,Nersisyan Hayk,Won, Chang-Whan,Kwon, Hyuk-Sang 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.9
Spinel phase $LiMn_2O_4$ is of great interest as cathode materials for lithium-ion batteries. In this study, SHS (Self propagating High-temperature Synthesis) method to synthesize spinel $LiMn_2O_4$ directly from lithium nitrate, manganese oxide, manganese and sodium chloride were investigated. The influence of Li/Mn ratio, the heat-treated condition of product have been explored. The resultant $LiMn_2O_4$ synthesized under the optimum synthesis conditions shows perfect spinel structure, uniform particle size and excellent electrochemical performances.
신창윤,원창환,Shin, Chang-Yun,Won, Chang-Whan 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.7
The preparation of FeB by SHS in $B_2O_3-Mg-Fe-Fe_3O_4$ system was investigated in this study. In the preparation of FeB, the effects of the initial pressure of inert gas in reactor, the content of Mg and $Fe_3O_4$ in mixture on the reactivity and reaction products was investigated. The minimum initial pressure of inert gas in reactor for SHS reaction in this system was 25 atm, and as the pressure increased, the concentration of unreacted Mg decreased and combustion temperature increased. At the initial inert gas pressure in reactor of 25 atm, the optimum composition for the preparation of pure FeB was $1.5B_2O_3$+3.43Mg+ 1.7Fe+$0.1Fe_3O_4$. The FeB synthesized in this condition had an irregular shape and the particle size of $5\;{\mu}m$.
고상법에 의한 Zn<sub>2</sub>SiO<sub>4</sub>:Mn<sup>2+</sup>녹색 형광체의 제조와 특성에 관한 연구
유현희,원형일,원창환,Yoo, Hyeon-Hee,Nersisyan, Hayk,Won, Hyung-Il,Won, Chang-Whan 한국재료학회 2011 한국재료학회지 Vol.21 No.6
[ $Zn_{2(1-x)}Mn_xSiO_4$ ]$0.07{\leq}x{\leq}0.15$) green phosphor was prepared by solid state reaction. The first heating was at $900^{\circ}C-1250^{\circ}C$ in air for 3 hours and the second heating was at $900^{\circ}C$ in $N_2/H_2$(95%/5%) for 2 hours. The size effect of $SiO_2$ in forming $Zn_2SiO_4$ was investigated. The temperature for obtaining single phase $Zn_2SiO_4$ was lowered from $1100^{\circ}C$ to $1000^{\circ}C$ by decreasing the $SiO_2$ particle size from micro size to submicro size. The effect of the activators for the Photoluminescence (PL) intensity of $Zn_2SiO_4:Mn^{2+}$ was also investigated. The PL intensity properties of the phosphors were investigated under vacuum ultraviolet excitation (147 nm). The emission spectrum peak was between 520 nm and 530 nm, which was involved in green emission area. $MnCl_2{\cdot}4H_2O$, the activator source, was more effective in providing high emission intensity than $MnCO_3$. The optimum conditions for the best optical properties of $Zn_2SiO_4:Mn^{2+}$ were at x = 0.11 and $1100^{\circ}C$. In these conditions, the phosphor particle shape was well dispersed spherical and its size was 200 nm.
자전연소반응법에 의해 제조된 PZT의 전기적 특성에 미치는 Sr의 영향
양범석,신창윤,원창환,Yang, Beom-Seok,Shin, Chang-Yun,Won, Chang-Whan 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.11
PSZT are selected and SHS are applied to each system. The sintering properties of PSZT powders showed $7.754g/cm^3$ of sintered density and $4{\mu}m$ of grain size at sintering temperature of $1250^{\circ}C$. Curie temperature lowered gradually from $363.6^{\circ}C\;to\;319.2^{\circ}C$ and relative dielectric constants increased rapidly by a quantity of Sr. This remarkable contrast in dielectric properties with powder preparation methods, in this study, was not due to grain size and sintered density but rather a crystallinity and sinterability of synthesized powders, extra-supplied Pb during reaction, mol fraction of rhombohedral phase and purity of starting materials.
이종현,강용,원창환,천병선,Lee, Jong-Hyeon,Kang, Yong,Won, Chang-Whan,Chun, Byong-Sun 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.5
Li-ferrite powders were prepared from mixture of Fe and Li salts using a hydrothermal method. Their crystal structure, microstructure and magnetic property were investigated with X-ray diffraction analysis, chemical analysis, SEM, and VSM. In the case of using FeCl3 as a precursor, Li-ferrite powders were synthesized. However, Fe3O4 was formed when the precursor was a divalented Fe2SO4 or FeCl2. The precipitation rate of Li-ferrite was increased as the reaction temperature increased. The optimum conditions of synthesis were the mole ratio of Fe+++/Li+=2, pH 13, the reaction temperature of 25$0^{\circ}C$ and the reaction time of 120min. With this condition, the spherical particles with good dispersion were obtained with average particle size of 0.4${\mu}{\textrm}{m}$ and saturation magnetization of 65 emu/g.
고상법에 의한 BaSrSiO<sub>4</sub> 형광체의 분말합성 및 발광특성
강주영,원형일,원창환,Kang, Joo Young,Won, Hyeong Il,Hayk, Nersisyan,Won, Chang Whan 한국재료학회 2013 한국재료학회지 Vol.23 No.12
In this study, green barium strontium silicate phosphor ($BaSrSiO_4:Eu^{3+}$, $Eu^{2+}$) was synthesized using a solid-state reaction method in air and reducing atmosphere. Investigation of the firing temperature indicates that a single phase of $BaSrSiO_4$ is formed when the firing temperature is higher than $1400^{\circ}C$. The effect of firing temperature and doping concentration on luminescent properties are investigated. The light-emitting property was the best when the molar content of $Eu_2O_3$ was 0.025 mol. Also, the luminescent brightness of the $BaSrSiO_4$ fluorescent substance was the best when the particle size of the barium was $0.5{\mu}m$. $BaSrSiO_4$ phosphors exhibit the typical green luminescent properties of $Eu^{3+}$ and $Eu^{2+}$. The characteristics of the synthesized $BaSrSiO_4:Eu^{3+}$, $Eu^{2+}$ phosphor were investigated using X-ray diffraction (XRD) and scanning electron microscopy. The maximum emission band of the $BaSrSiO_4:Eu^{3+}$, $Eu^{2+}$ was 520 nm.